Planing machines are used in the lumber industry to plane lumber, giving different pieces of wood specific profiles. Automatic planing machines usually include a feed table, upper and lower planing heads, a linebar, and right and left side planing heads. The feed table is used for the preliminary vertical positioning of the lumber with respect to the upper and lower planing heads. The linebar is usually fixed and is used to laterally guide the lumber along a travelling course in the planing machine. The side planing heads, usually right and left, are used to plane the side surfaces of the lumber. They define a planing width therebetween. An example of an automated planing machine is disclosed in U.S. Pat. No. 6,666,246 (GILBERT).
Conventional planing heads generally include a cylindrical body and a plurality of blade receiving portions around its periphery. Such blade receiving portions generally include a transverse groove for receiving a wedge grip and blade. A wedge grip retains each blade within a groove and can translate radially therewithin. In use, the rotation of the planing head forces the wedge grips outward under the effect of the centrifugal force. In doing so, the wedge grips press against angled surfaces within each groove and the resultant force pushes the wedge grips toward their respective blades to hold them in place. When the planing head is at rest, the gripping effect is lessened and the blades can be removed as desired. The centrifugal effect can be complemented by additional components in or around the groove such as a mounting strip or a spring-loaded bolt (shown respectively in U.S. Pat. No. 5,904,193 (KELLNER) and U.S. Pat. No. 6,279,444 (KELLNER et al.)).
It is also known in the art to apply additional pressure from underneath the blades to complement the centrifugal effect. Channels are provided within the body of the planing head in which grease or oil is inserted and pressurised. Generally, a main channel forming a ring inside the cylindrical body of the planing head receives the grease or oil and distributes it to radial connecting channels under each blade. The grease or oil pressure pushes a piston outward under each wedge grip, thereby reinforcing the force of the wedge grip on the blade.
One drawback of this latter system is that the body of such a conventional planing head is manufactured from two concentric cylindrical pieces in order to form the main channel, which is provided at the junction between the two pieces. This adds complexity to the manufacturing process and involves higher costs than for a planing head body manufactured from a single piece. In addition, and as will be understood by one of ordinary skill in the art, a planing head body constructed from two concentric cylindrical pieces will not be as solid as a similarly sized one-piece construction.
There is therefore a need for an improved planing head and method of manufacture thereof which does not require the use of two concentric pieces in order to form the body of the planing head.